Display device

ABSTRACT

A display device comprising means for forming a discharge space including a plurality of discharge electrodes constituting an electron source, a plurality of first control grids arranged in parallel for controlling the electron beam generated from the discharge space, a plurality of second control grids arranged in parallel with each other and at right angles to said first control grids, means for accelerating the electron beam controlled by said first and second control grids, a phosphor illuminated by the impingement thereupon of the accelerated electron beam, means for applying to said second control grids pulse voltages in sequence, means for applying a pulse voltage to said discharge electrodes to effect a discharge only in the space corresponding to the control grid to which the pulse voltage is applied, and means for applying a pulse-width-modulated voltage to said first control grids.

United States Patent 11 1 Yamane et a1. Apr. 2, 1974 [5 DISPLAY DEVICE 3,753,041 8/1973 Lustig 315/169 R [75] Inventors: Mikiya Yamane, Kunitachi; Seiichi Nu Kokubunji; Tsuyoshi Primary Examiner-Herman Karl Saalbach S k Musashimurayama; Tetsunori Assistant Examiner-Lawrence J. Dahl K ji, K k b ji; M hi Attorney, Agent, or Firm-Craig and Antonelli Mizushima, Hachioji; Shinichi Shinada, Kokubunji; Tsune 57 ABSTRACT Miyashita, Hachioji, all of Japan 1 A display device comprising means for forming a dis- [73] Asslgnee' Tokyo Japan charge space including a plurality of discharge elec- [22] Fil d; F b, 15, 1973 trodes constituting an electron source, a plurality of first control grids arranged in parallel for controlling [21] Appl 332545 the electron beam generated from the discharge space, a plurality of second control grids arranged in [30] Foreign Application Priority Data parallel with each other and at right angles to said first Feb. 25 1972 Japan 47-18946 comm] grids means for accelerating the electron beam controlled by said first and second control grids, a phosphor illuminated by the impingement thereupon [52] US. Cl..... 315/169 TV, 178/73 D, 313/108 B,

313/1095, 315/169 R of the accelerated electron beam, means for applying 511 1m. (:1. 110411 3/16 HOSb 37/00 Said Sewn! Comm grids Pulse vOltages 58 Field of Search 178/7 3 D 7 s D' means applying a Pulse "wage Said 313/108 5. 5 R charge electrodes to effect a discharge only in the space corresponding to the control grid to which the [56] References Cited pulse voltage is applied, and means for applying a UNITED STATES PATENTS pulse-width-modulated voltage to said first control rids. 3,176,184 3/1965 Hopkins 315/169 R X g 3,579,015 5/1971 Gregory 178/7.5 D 1 Claim, 3 Drawing Figures POWER SUPPLY 2 1 11 30 4-1 4-11 4:2 2 Q POWER 257 2 8 t SUPPLY 20 H T HORIZGJTAL L L?N F L1NE w l l: i. lg scmwme DRIVING 7-2: 2 c cu 'CIRCUIT 7 '1 l L l l8-N 1112 omvms CIRCUIT PULSE- XO 8 L1EATIQM- CIRCUIT GATE W cmcun 24 DELAY ,o--- 22 ClRCUIT PATENTEDAPR 2:914 3301.864

' SHEET 1 BF 3 FIG.

PAIENIEDIPII 2 1974 .3 8 O 1.8 64

' SHEET 2 [IF 3 4-I 74 I R 4-2 F 2 POWER 27 28 L SUPPLY 2O HORIZONTAL HORIZONTAL LINE LINE SCANNING DRIVING CIRCUIT CIRCUIT vERgIcAL LIN DRIVING 26 CIRCUIT 1 PU -SE WIDTH MODULATION CIRCUIT DELAY CIRCUIT PATENTEDAPR 2 I974 3. 8 0 1 Q 864 sum a nr 3 FIG. 3

VOLTAGE BETWEEN Vd IT-I AND I8-I VOLTAGE AT Vd T I7-2 AND I8-2 VOLTAGE AT Vd l7-4 AND l8-4 I O i POTENTIAL AT 7-l AGAINST 9 POTENTIAL AT 7-2 TTTTTTTTTTT AGAINST 9 g POTENTIAL AT 7-3 AGAINST 9 POTENTIAL AT 7-4 AGAINST 9 DISPLAY DEVICE The present invention relates to a display device for use in a television or the like or more in particular to a display device using gaseous discharge as an electron source.

A well known conventional display device comprises a vacuum housing in which are arranged grid wires, a phosphor and a cathode for electron emission. In such a conventional device, the cathode is such that it is impossible to emit electrons uniformly over a wide area, resulting in an unsatisfactory display of images.

One possible approach to such a problem of the conventional device is to produce electrons over a wide area by the use of gaseous discharge. The use of the gaseous discharge is deemed to enable a large current to be obtained over a wider area than in the thermionic emission of electrons and enable response time to be improved.

Even if the discharge is always effected over the whole area of a predetermined discharge space, only a small percentage of the released electrons is used for display of an image, resulting in a low efficiency.

Accordingly, it is an object of the present invention to provide a display device which is capable of displaying an image with a high efficiency by efficiently using the electrons released by the gaseous discharge.

In order to achieve the above-mentioned object, the present invention is characterized by the fact that a control voltage is applied to a line at a time and a discharge voltage in synchronism with the control voltage is applied to that discharge electrode for effecting a discharge only in the portion of the discharge space corresponding to the control grid to which the control voltage is applied.

The above and other objects, features and advantages will be made apparently by the detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagram showing the construction of the display device according to the present invention;

FIG. 2 is a block diagram showing an embodiment of the present invention; and

FIG. 3 is a diagram of waveforms for explaining the operation of the embodiment of FIG. 2.

Referring to FIG. 1 showing the construction of the display device according to the invention employing a gaseous discharge for electron source, reference numeral 1 shows a transparent insulating plate of glass or the like, numeral 2 a transparent conductive film of NESA film (trade mark) or the like laid on the surface of the transparent insulating plate 1, numeral 3 a phosphor layer applied on the transparent conductive layer 2, numeral 4, including numerals 4-1, 4-2 and 4-3, first control grids arranged in parallelwith each other on a plane almost in parallel with the phosphor layer 3, numeral 5 a first insulating frame, numeral 6 an accelerating space formed in the first insulating frame 5, numeral 7, including the numerals 7-1, 7-2 and 7-3, second control grids arranged in parallel with each other at right angles to the first control grids 4, numeral 8 a first insulating separator inserted between the first control grids 4 and the second control grids 7, numeral 9 a conductive shielding plate, numeral 10 a second insulating separator inserted between the second control grids 7 and the conductive shielding plate 9, numeral 11 a second insulating plate, numeral 12 a discharge space formed in the second insulating frame 11, numeral 13 an insulating plate, and numerals 14, 15 and 16 apertures bored in those points of the first and second insulating separators and the conductive shielding plate where the control grids intersect each other. By way of explanation, the apertures and areas surrounding them will be referred to as a control space. Reference numerals 17 and 18, including numerals 17-1, 17-2, l7-3, 18-1, 18-2 and 18-3, show discharge electrodes for releasing electrons in the discharge space 12. The accelerating space 6, the discharge space 12 and the control space are hermetically sealed, each containing inert gas, silver vapor or mixed gas thereof.

In the device with the above-described construction, a voltage is applied between the discharge electrodes 17 and 18 thereby to effect gaseous discharge in the discharge space 12. The electrons released by the gaseous discharge are passed by diffusion to the control space through the apertures bored in the conductive shielding plate 9. In the process, if a bias voltage which is negative with respect to the conductive shielding plate 9 is applied to the second control grids 7, the electrons are attracted back to the conductive shielding plate 9. In this case, application to a specified grid, say, the grid 7-1 among the control grids 7 of a voltage which is positive or zero with respect to the negative bias voltage (such negative or zero voltage is hereinafter referred to as a control voltage) causes the electron beam to pass through only those apertures 15 in the insulating plate 10 which correspond to the control grid 7-1. When the control voltage is applied only to a specified one of the first control grids 4, electrons are accelerated to pass into the accelerating space through only those apertures of the insulating plate 8 involving the first and second control grids to which the control voltage is applied. Those electrons are accelerated in the accelerating space by the high voltage 12 applied to the transparent conductive film 2 and impinge upon the phosphor with high energy thereby to illuminate it. Accordingly, it is possible to display a television image due to an image signal by employing a signal corresponding to an image signal such as pulse-width modulated signal as the control voltage applied to either the first grids or second grids.

In this way of generating electrons by gaseous discharge, differing from the conventional method in which the thermionic emission is used with the cathode as an electron source, electrons are obtained uniformly from over a wide area, thereby making it possible to produce a large current. Further, the use of the gaseous discharge permits the response character .to be improved remarkably.

In this connection, the continuous discharge in the whole discharge area in the discharge space results in only a small part of the released electrons being consumed in the display operation, wasting much of the power for reduced efficiency.

This problem is obviated in the following-described embodiment of which the block diagram is illustrated in FIG. 2. In this embodiment, an image is displayed by the pulse-width modulation in which the image signal corresponding to the image to be displayed is represented by a pulse width equivalent to the level of the image signal. In the drawing, the reference numeral 19 generally shows the display device according to the invention as shown in FIG. 1 which includes the discharge electrodes 17 and 18, the first control grids 4 and the second control grids 7. Each of the discharge electrodes 17 is independent of each other, while the other electrodes 18 are connected with each other. Reference numeral 20 shows an input terminal for vertical synchronizing signals, numeral 21 an input terminal for horizontal synchronizing signals, numeral 22 an input terminal for image signals, and numeral 23 a delay circuit or line with a delay time equal to the horizontal scanning period or the period required for generation of the horizontal synchronizing signal. The delay circuit 23 has output terminals in the number of M corresponding to the grids 4-1, 4-2, 4-3, 4-M. Reference numeral 25 shows a pulse width modulation circuit containing an analog memory, numeral 26 a vertical line driving circuit driven by the output of the pulse width modulation circuit 25, numeral 27 a horizontal line scanning circuit driven by the horizontal synchronizing signal which is provided with output terminals in the number of N corresponding to the second control grids 7-l, 72, 73, 7N, numeral 28 a horizontal line driving circuit with its input signal provided by the scanning pulse from the horizontal line scanning circuit, numeral 29 a power supply for generating discharge voltages in sequence at the N output terminals periodically in synchronism with the horizontal synchronizing signal, and numeral 30 another power supply for applying a high voltage to the transparent conductive film 2. Some of the outputs of the discharge power supply 29 are applied to the independent discharge electrodes 17-1, 17-2, l7-L, while the other outputs thereof are applied to the commonlyconnected discharge electrodes 18-1, 182, l8-L.

After the passage of a period equal to the horizontal scanning period following the application of a video signal to the input terminal 22 of the delay circuit 23, the video signal for one horizontal scanning period is distributed over the delay circuit. Under this condition, application of a horizontal synchronizing signal to the gate circuit 24 through the terminal 21 causes each of the gates to conduct, so that a signal appearing at each of the output terminals of the delay circuit 23 is applied to each input terminal of the pulse width modulation circuit 25 are converted into M signals of the same amplitude but with widths different according to their lev- 1 els, which pulses are amplified by the vertical line driving circuits 25 and applied to the first control grids 4-1, 4-2, 4-M. On the other hand, the vertical synchronizing signal obtained through the terminal 20 and the horizontal synchronizing signal produced through the terminal 21 drive the horizontal line scanning circuit 27, whereupon the output terminals thereof in the number of N corresponding to the second grids 7-1, 72, 7N produce sequential scanning pulses at an interval approximate to the horizontal scanning period. The scanning pulses are amplified by the horizontal line driving circuit 28 and applied to the second control grids 71, 72, 7N in sequence.

Discharge pulse voltages are produced from the power supply in synchronism with the scanning pulses applied sequentially to the second control grids 7-1, 72, 7-3, 7N or the horizontal synchronizing signal for driving the horizontal scanning circuit. The discharge pulse voltages are applied to the discharge electrodes l7 and 18. In view of the fact that the discharge electrodes l7-l, 17-2, l7-N are connected to the output terminals of the power supply 29 independently of each other through the lines [-1, l-2, l-N, while to that discharge electrode corresponding to the control grid to which the scanning pulse is applied. Therefore, each time the scanning pulse is generated, a discharge voltage is supplied in sequence from the discharge power supply through the lines l-l, l-2, lN, with the result that the discharge voltage and the scanning pulses which are control voltages applied to the second grids 71, 72, 7N assume the phase relationship as shown in FIG. 4.

It will be apparent from this diagram that during the period from t to t the control voltage is applied only to the grid 71 and the potential thereof is zero while the potentials of the grids 72, 73, 7N with respect to the conductive shielding plate 9 are negative and take the value of V As a result, it is only those electrons diffused by way of those of the apertures 16 bored in the conductive shielding plate 9 which correspond to the grid 71 that are capable of entering the control space. Also, during this period, the discharge voltage is applied to the discharge electrodes 17-1 and 18-1 respectively through the lead wires l-l and l, and therefore a discharge occurs and plasma exists only in that portion of the discharge space which corresponds to the grid 71.

The control voltage is applied only to the grid 72 and the discharge voltage applied only to to the discharge electrodes 17-2 and l8 2 during the period from t, to t In like manner, not only the control voltage but the discharge voltage are applied in sequence in the subsequent processes.

In this way, during the application of the control voltage, discharge occurs only in that portion of the discharge space corresponding to the control grid to which the control voltage is applied, whereby electrons generated by the discharge are efficiently used and wasteof electric power in the discharge space 12 is eliminated.

Even though the embodiment of FIG. 1 involves three grids and three discharge electrodes, it is needless to say that it is possible to manufacture a display device with n grids and n discharge electrodes with the same advantages. Further, an AC instead of DC voltage may be employed as the discharge voltage.

In the case where the width of the plasma generated by the discharge in the discharge space is larger than the interval between the control grids, a set of discharge electrodes may be usually provided for a plurality of the control grids in the-number of, say, m. In such a case, it is also needless to say that is suffices to apply the discharge voltage to the same set of discharge electrodes during the scanning of the m control grids.

It will be understood from the above description that according to the present invention the use of electric discharge as a source of electrons permits uniform brightness to be achieved over the whole area of the display face of the display device, greatly contributing to an improved efficiency.

What we claim is:'

1. A display device comprising a first insulating member for forming a discharge space for effecting gaseous discharge, said first insulating member being provided with a plurality of discharge electrodes as a source of electrons, a second insulating member for hermetically sealing said discharge space, a conductive member provided with a plurality of small apertures through which an electron beam from said discharge space is adapted to be passed, a third insulating member for forming an accelerating space for accelerating the electron beam passing through said plurality of small apertures, a transparent insulating member for hermetically sealing said accelerating space, first and second control grids interposed between said conductive member and said third insulating member for controlling the entrance of said electron beam into said accelerating space, said control grids intersecting each other at the positions corresponding to said small apertures, an insulating separator provided with a plurality of small apertures at the positions corresponding to those of said small apertures in said conductive member in sucha manner that said first and second control grids in certain spaced relationship intersect, a phosphor formed on said transparent insulating member, a transparent electrode formed intermediate said transparent insulating memher and said phosphor for causing an electron beam from said accelerating space to impinge upon said phosphor, means for supplying sequential control pulses to said plurality of second control grids, a power supply for generating a discharge voltage in synchronism with said control pulse applied to said second control grids, means connected with said power supply for applying said discharge voltage only to the discharge electrode in the portion of said discharge space corresponding to said second control grids to which said control pulse is applied, means for applying to said first plurality of control grids a signal which is pulsemodulated from a predetermined display signal in accordance with the level of each pulse of said display signal, and means for applying a high voltage to said transparent electrode for accelerating the electron beam in said accelerating space, whereby a gaseous discharge occurring in that portion of said discharge space which corresponds to said second control grid to which said control voltage is applied. 

1. A display device comprising a first insulating member for forming a discharge space for effecting gaseous discharge, said first insulating member being provided with a plurality of discharge electrodes as a source of electrons, a second insulating member for hermetically sealing said discharge space, a conductive member Provided with a plurality of small apertures through which an electron beam from said discharge space is adapted to be passed, a third insulating member for forming an accelerating space for accelerating the electron beam passing through said plurality of small apertures, a transparent insulating member for hermetically sealing said accelerating space, first and second control grids interposed between said conductive member and said third insulating member for controlling the entrance of said electron beam into said accelerating space, said control grids intersecting each other at the positions corresponding to said small apertures, an insulating separator provided with a plurality of small apertures at the positions corresponding to those of said small apertures in said conductive member in such a manner that said first and second control grids in certain spaced relationship intersect, a phosphor formed on said transparent insulating member, a transparent electrode formed intermediate said transparent insulating member and said phosphor for causing an electron beam from said accelerating space to impinge upon said phosphor, means for supplying sequential control pulses to said plurality of second control grids, a power supply for generating a discharge voltage in synchronism with said control pulse applied to said second control grids, means connected with said power supply for applying said discharge voltage only to the discharge electrode in the portion of said discharge space corresponding to said second control grids to which said control pulse is applied, means for applying to said first plurality of control grids a signal which is pulse-modulated from a predetermined display signal in accordance with the level of each pulse of said display signal, and means for applying a high voltage to said transparent electrode for accelerating the electron beam in said accelerating space, whereby a gaseous discharge occurring in that portion of said discharge space which corresponds to said second control grid to which said control voltage is applied. 